Why do deep-sea fish glow?

Answer: Bioluminescence for survival

From eating glowing bacteria — Wrong. While some fish do host light-producing bacteria, many create light themselves through chemical reactions in specialized organs called photophores.

Bioluminescence for survival ✓ — Correct! Deep-sea fish use bioluminescence to find mates, lure prey, confuse predators, or camouflage against faint surface light. In the pitch-black deep ocean, making your own light is a powerful survival tool!

Reflection of surface light — Wrong. No sunlight reaches the deep sea—it's completely dark below 1,000 meters. Fish must produce their own light through chemical reactions called bioluminescence.